clk: sunxi-ng: nm: Support finding closest rate

Use the helper function ccu_is_better_rate() to determine the rate that
is closest to the requested rate, thereby supporting rates that are
higher than the requested rate if the clock uses the
CCU_FEATURE_CLOSEST_RATE.

Add the macro SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_CLOSEST which
sets CCU_FEATURE_CLOSEST_RATE.

To avoid code duplication, add the macros
SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_FEAT that allows selecting
arbitrary features and use it in the original
SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX as well as the newly introduced
SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_CLOSEST macros.

Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
Link: https://lore.kernel.org/r/20230807-pll-mipi_set_rate_parent-v6-6-f173239a4b59@oltmanns.dev
Signed-off-by: Chen-Yu Tsai <wens@csie.org>

Author: Frank Oltmanns

drivers/clk/sunxi-ng/ccu_nm.c

@@ -27,8 +27,8 @@ static unsigned long ccu_nm_calc_rate(unsigned long parent,
 	return rate;
 }
 
-static unsigned long ccu_nm_find_best(unsigned long parent, unsigned long rate,
-				      struct _ccu_nm *nm)
+static unsigned long ccu_nm_find_best(struct ccu_common *common, unsigned long parent,
+				      unsigned long rate, struct _ccu_nm *nm)
 {
 	unsigned long best_rate = 0;
 	unsigned long best_n = 0, best_m = 0;
@@ -39,10 +39,7 @@ static unsigned long ccu_nm_find_best(unsigned long parent, unsigned long rate,
 			unsigned long tmp_rate = ccu_nm_calc_rate(parent,
 								  _n, _m);
 
-			if (tmp_rate > rate)
-				continue;
-
-			if ((rate - tmp_rate) < (rate - best_rate)) {
+			if (ccu_is_better_rate(common, rate, tmp_rate, best_rate)) {
 				best_rate = tmp_rate;
 				best_n = _n;
 				best_m = _m;
@@ -159,7 +156,7 @@ static long ccu_nm_round_rate(struct clk_hw *hw, unsigned long rate,
 	_nm.min_m = 1;
 	_nm.max_m = nm->m.max ?: 1 << nm->m.width;
 
-	rate = ccu_nm_find_best(*parent_rate, rate, &_nm);
+	rate = ccu_nm_find_best(&nm->common, *parent_rate, rate, &_nm);
 
 	if (nm->common.features & CCU_FEATURE_FIXED_POSTDIV)
 		rate /= nm->fixed_post_div;
@@ -210,7 +207,7 @@ static int ccu_nm_set_rate(struct clk_hw *hw, unsigned long rate,
 					   &_nm.m, &_nm.n);
 	} else {
 		ccu_sdm_helper_disable(&nm->common, &nm->sdm);
-		ccu_nm_find_best(parent_rate, rate, &_nm);
+		ccu_nm_find_best(&nm->common, parent_rate, rate, &_nm);
 	}
 
 	spin_lock_irqsave(nm->common.lock, flags);

drivers/clk/sunxi-ng/ccu_nm.h

@@ -108,15 +108,16 @@ struct ccu_nm {
 		},							\
 	}
 
-#define SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX(_struct, _name,	\
+#define SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_FEAT(_struct, _name,	\
 						 _parent, _reg,		\
 						 _min_rate, _max_rate,	\
 						 _nshift, _nwidth,	\
 						 _mshift, _mwidth,	\
 						 _frac_en, _frac_sel,	\
 						 _frac_rate_0,		\
 						 _frac_rate_1,		\
-						 _gate, _lock, _flags)	\
+						 _gate, _lock, _flags,	\
+						 _features)		\
 	struct ccu_nm _struct = {					\
 		.enable		= _gate,				\
 		.lock		= _lock,				\
@@ -129,14 +130,55 @@ struct ccu_nm {
 		.max_rate	= _max_rate,				\
 		.common		= {					\
 			.reg		= _reg,				\
-			.features	= CCU_FEATURE_FRACTIONAL,	\
+			.features	= _features,			\
 			.hw.init	= CLK_HW_INIT(_name,		\
 						      _parent,		\
 						      &ccu_nm_ops,	\
 						      _flags),		\
 		},							\
 	}
 
+#define SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX(_struct, _name,	\
+						 _parent, _reg,		\
+						 _min_rate, _max_rate,	\
+						 _nshift, _nwidth,	\
+						 _mshift, _mwidth,	\
+						 _frac_en, _frac_sel,	\
+						 _frac_rate_0,		\
+						 _frac_rate_1,		\
+						 _gate, _lock, _flags)	\
+	SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_FEAT(_struct, _name,	\
+						_parent, _reg,		\
+						_min_rate, _max_rate,	\
+						_nshift, _nwidth,	\
+						_mshift, _mwidth,	\
+						_frac_en, _frac_sel,	\
+						_frac_rate_0,		\
+						_frac_rate_1,		\
+						_gate, _lock, _flags,	\
+						CCU_FEATURE_FRACTIONAL)
+
+#define SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_CLOSEST(_struct, _name, \
+						 _parent, _reg,		\
+						 _min_rate, _max_rate,	\
+						 _nshift, _nwidth,	\
+						 _mshift, _mwidth,	\
+						 _frac_en, _frac_sel,	\
+						 _frac_rate_0,		\
+						 _frac_rate_1,		\
+						 _gate, _lock, _flags)	\
+	SUNXI_CCU_NM_WITH_FRAC_GATE_LOCK_MIN_MAX_FEAT(_struct, _name,	\
+						_parent, _reg,		\
+						_min_rate, _max_rate,	\
+						_nshift, _nwidth,	\
+						_mshift, _mwidth,	\
+						_frac_en, _frac_sel,	\
+						_frac_rate_0,		\
+						_frac_rate_1,		\
+						_gate, _lock, _flags,	\
+						CCU_FEATURE_FRACTIONAL |\
+						CCU_FEATURE_CLOSEST_RATE)
+
 #define SUNXI_CCU_NM_WITH_GATE_LOCK(_struct, _name, _parent, _reg,	\
 				    _nshift, _nwidth,			\
 				    _mshift, _mwidth,			\